1. Field of the Invention
This invention relates to a chemical mechanical polishing composition, more particularly to a chemical mechanical polishing composition that can prevent undesired metal residue and dishing effect on a wafer surface.
2. Description of the Related Art
Chemical mechanical polishing is a technique for removing defects on a wafer surface so as to achieve planarity of the surface, thereby eliminating focusing problems during photolithography process. The chemical mechanical polishing technique was originally used in manufacturing micro devices having a size less than 0.5 micron. However, with the current trend of minimization of devices, chemical mechanical polishing technique has been widely employed in the industry.
In the process for manufacturing an integrated circuit, a polishing process is employed to planarize an interlayer (e.g., silicon oxide and silicon nitride), and a metal wire used to connect active devices. The method for polishing a metal wire, e.g., tungsten, copper, aluminum, etc., includes the steps of disposing a semiconductor wafer on a polishing stage provided with a polishing head, and applying an abrasive particle-containing slurry to a surface of the semiconductor wafer so as to improve polishing efficiency. Two mechanisms can be chosen for polishing the metal wire using the slurry composition. In the first mechanism, components in the slurry composition react with the metal wire to continuously form an oxide layer on the metal surface, and the abrasive particles in the slurry composition act to polish and to remove the oxide layer. An oxidizing agent is generally required in the first mechanism. In the second mechanism, no protective oxide layer is formed. Instead, the components in the slurry composition attack and dissolve the metal, and the mechanical action of the abrasive particles enhances the dissolution rate so as to reduce the thickness of the metal wire. Because of the uneven polishing problem in the CMP process, undesired dishing effect and undesired metal residue on the wafer surface tend to take place.
U.S. Pat. No. 6,447,563 discloses a slurry system used for polishing metal layers. The slurry system includes a first part and a second part, and has a pH value ranging from 2 to 11. The first part comprises a dispersion solution consisting essentially of an abrasive, a stabilizing agent, and a surfactant. The second part comprises an activator solution, free of abrasives, having at least two components selected from the group consisting of an oxidizer, acids, amines, chelating agent, fluorine-containing compounds, corrosion inhibitors, biological agents, surfactants, buffering agents, and mixtures thereof. The acid in the activator solution of the second part can be an organic acid, such as formic acid, acetic acid, lactic acid, etc., or an inorganic acid, such as hydrochloric acid, sulfuric acid, etc. Preferred acids are those containing one or more carboxylic acid groups substituted with hydroxyl groups, such as malic acid, tartaric acid, gluconic acid, and citric acid. In addition, the surfactant can be non-ionic, anionic, cationic, or amphoteric surfactant. In the example 1 of this patent, a slurry system constituted of 4 wt % fumed silica, 1 wt % H2O2, and 0.1 molar propanoic acid was used to polish a copper wafer. The removal rate was greater than 450 nm and the non-uniformity was less than 5%. This patent primarily focuses on the improvement of the polishing rate. The problem of the metal residue on the wafer surface is not addressed in this patent.
U.S. Pat. No. 6,846,177 discloses a method for manufacturing a metal line contact plug of a semiconductor device by a Chemical Mechanical Polishing (CMP) process. The method includes the steps of: (1) performing a first CMP process using a first slurry solution including 1 to 20 wt % of abrasive, 0.1 to 15 wt % of oxidizer, and 0.01 to 10 wt % of complexing agent based on the total weight of the first slurry solution, and having an etching selectivity of more than 10 for a metal/insulating film and a pH ranging from 2 to 9; and (2) performing a second CMP process using a second slurry solution including 5 to 30 wt % of abrasive and 0.01 to 5 wt % of oxidizer based on the total weight of the second slurry solution, and having an etching selectivity of less than 3 for the metal/insulating film and a pH ranging from 6 to 12. The complexing agent of the first slurry solution is selected from the group consisting of citric acid, tartaric acid, succinic acid, malic acid, maleic acid, fumaric acid, malonic acid, EDTA, glycolic acid, salts thereof, and mixtures thereof. This patent solves the problem that a metal line contact plug is not separated well. The problems caused by the uneven polish are not mentioned.
TW patent publication No. 574352 discloses a slurry composition for Chemical Mechanical Polishing (CMP) process and use thereof. The slurry composition includes 70 to 99.5 wt % of aqueous solvent, 0.1 to 25 wt % of abrasive particles, 0.01 to 1 wt % of corrosion inhibitor, and 0.01 to 1 wt % of chemicals. The chemicals are selected from the group consisting of compounds having the following formulas:
and the combination thereof, wherein X, Y, and Z are independently selected from the group consisting of: H and C1-C6 alkyl. The object of this reference is to prevent copper dishing.
Since the components of the slurry composition for CMP process have great effect on the polishing rate, dishing degree, and metal residue on the wafer surface, there is a need in the art to provide a composition that can eliminate the problems of metal dishing and metal residue while maintaining desired polishing rate.